Decorative sheet, and decorative resin-molded article employing same

ABSTRACT

The invention provides a decorative sheet including at least a surface protective layer on a substrate, in which the surface protective layer includes a cured material of an ionizing radiation curable resin composition at least containing a polycarbonate(meth)acrylate (A) and a multi-functional (meth)acrylate (B) in a mass ratio (A)/(B) of (98/2)-(70/30). The invention also provides a decorative sheet including at least a surface protective layer on a substrate, in which the surface protective layer includes a cured material of an ionizing radiation curable resin composition at least containing an acrylic silicone (meth)acrylate (C) and a multi-functional (meth)acrylate (B) in a mass ratio (C)/(B) of (50/50)-(95/5). The present invention provides a decorative sheet with a surface protective layer having scratch resistance as well as three-dimensional formability.

TECHNICAL FIELD

The present invention relates to a decorative sheet with a surfaceprotective layer consisting of a cured material of a specific ionizingradiation curable resin composition.

BACKGROUND ART

A decorative resin-molded article decorated by laminating a decorativesheet on the surface of a molded article is used in various applicationssuch as automotive interior parts. The method of forming such adecorative resin-molded article includes insert molding in which adecorative sheet is first three-dimensionally formed with a vacuumforming mold, the molded sheet is inserted in an injection mold, andthen a fluid state of resin is injected in the injection mold tointegrate the resin with the molded sheet (for example, see Patentdocument 1); and simultaneous injection-molding and decoration in whicha decorative sheet inserted in a mold is integrated with a melted resininjected in a cavity during injection molding to decorate the surface ofthe resin compact (for example, Patent documents 2 and 3).

The above-mentioned decorative resin-molded article is provided with asurface protective layer in order to improve the scratch resistance onthe surface. However, the above-mentioned method of forming such adecorative resin-molded article has a problem in the process ofthree-dimensionally forming a decorative sheet with a vacuum formingmold in insert molding and in the process of drawing and firmlyattaching a decorative sheet along the inner periphery of a cavityduring preforming or during injecting a melted resin in simultaneousinjection-molding and decoration. This problem causes the decorativesheet to be drawn more than minimum requirement to fit the shape of themold due to the effect of vacuum or compressed air or due to the tensiongenerated by the pressure and the shear stress of the melted resin,resulting in a crack generated on the surface protective layer of thecurved surface of a molded article.

To approach the above-mentioned problem, an ionizing radiation curableresin such as an ultraviolet curable resin has been used as the surfaceprotective layer for improving the crosslink density of the resinforming the surface protective layer of a decorative sheet so as toattempt to improve the abrasion resistance and the scratch resistance ofthe surface of a decorative resin-molded article. However, the problemof a crack generated on the curved surface of a molded article duringforming still exists.

Alternatively, an ionizing radiation curable resin such as anultraviolet curable resin used as the surface protective layer has beenattempted to be half-cured at the stage of a decorative sheet and thenfully cured after decorative molding (see Patent document 4). However,problems are created, in which the surface protective layer containingan uncured resin component is easily scratched and hardly handled and inwhich the mold is contaminated due to the uncured resin componentadhering to the mold. To solve these problems, a protection film may beprovided on a half-cured surface protective layer, but this methodcomplicates the manufacturing process and causes cost increases.

Therefore, the surface protective layer with scratch resistance as wellas three-dimensional formability is desired.

A resin composition containing a polycarbonate(meth)acrylate is known(for example, Patent documents 5-10), and a resin composition containinga small amount of yellowing polycarbonate urethane acrylate oligomer isused for the inner colored sheet on the back side of the surfacetransparent sheet of a decorative sheet for insert molding (Patentdocument 11). However, no polycarbonate(meth)acrylates are used for thesurface protective layer of a decorative sheet.

An acrylic silicon resin has the structure in which the acrylic polymerchain is strongly cross-linked by a siloxane bond, providing excellentweatherability, heat resistance, chemical resistance, and waterresistance so as to be widely used in exterior paint. However, if anacrylic silicon resin is used as the surface protective layer in orderto improve the scratch resistance on the surface of a resin-moldedarticle, the formed film becomes hard and fragile, possibly causing acrack. To prevent a crack from being generated, a curing process such asultraviolet curing is applied to a sheet for insert molding after vacuumforming or to a resin molded article after injection molding when anacrylic silicon resin is used as the surface protective layer (forexample, see Patent documents 12-14).

However, the curing process applied to a three-dimensionally moldedarticle is complicated with poor economical efficiency, hardly providinguniform curing.

Therefore, the surface protective layer, which has three-dimensionalformability as well as scratch resistance while maintaining theexcellent chemical resistance of the acrylic silicon resin, is desired

CITATION LIST

Patent document 1: JP 2004-322501 A

Patent document 2: JP S50-19132 A

Patent document 3: JP S61-17255 A

Patent document 4: JP H6-134859 A

Patent document 5: JP S64-24809 A

Patent document 6: JP H3-181517 A

Patent document 7: JP H7-44913 A

Patent document 8: JP 2000-53887 A

Patent document 9: JP 2000-198840 A

Patent document 10: JP 2000-351843 A

Patent document 11: JP 2003-145573 A

Patent document 12: JP H6-57199 A

Patent document 13: JP H6-100799 A

Patent document 14: JP H6-287470 A

DISCLOSURE OF THE INVENTION

An objective of the present invention is to provide a decorative sheetwith a surface protective layer having scratch resistance as well asthree-dimensional formability under such a situation.

As a result from the extensive studies to achieve a solution to theabove-mentioned problem, the inventors have found that the surfaceprotective layer of a decorative sheet consists of a cured material of aspecific ionizing radiation curable resin composition can solve thisproblem. The present invention is achieved based on this finding.

The present invention provides:

(1) a decorative sheet comprising at least a surface protective layer ona substrate, in which the surface protective layer includes a curedmaterial of an ionizing radiation curable resin composition at leastcontaining a polycarbonate(meth)acrylate (A) and a multi-functional(meth)acrylate (B) in a mass ratio (A)/(B) of (98/2)-(70/30);(2) a decorative sheet comprising at least a surface protective layer ona substrate, in which the surface protective layer includes a curedmaterial of an ionizing radiation curable resin composition at leastcontaining an acrylic silicone (meth)acrylate (C) and a multi-functional(meth)acrylate (B) in a mass ratio (C)/(B) of (50/50)-(95/5); and(3) a decorative resin-molded article formed by using the decorativesheet according to the above-mentioned (1) or (2).

The decorative sheet of the present invention can provide a decorativeresin-molded article with excellent scratch resistance and easythree-dimensional formability with no cracks being generated on thesurface protective layer in insert molding and in simultaneousinjection-molding and decoration because the surface protective layerhas excellent scratch resistance as well as excellent three-dimensionalformability and also has excellent chemical resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a pattern diagram illustrating the cross section of anaspect of the decorative sheet of the present invention.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

The decorative sheet of the first embodiment of the present inventionincludes at least a surface protective layer on a substrate, in whichthe surface protective layer includes a cured material of an ionizingradiation curable resin composition at least containing apolycarbonate(meth)acrylate (A) and a multi-functional (meth)acrylate(B) in a mass ratio (A)/(B) of (98/2)-(70/30).

The ionizing radiation curable resin composition is referred herein toas a composition containing an ionizing radiation curable resin. Theionizing radiation curable resin has an energy quantum capable ofcross-linking and polymerizing molecules in electromagnetic radiation orcharged particle radiation. Specifically, the ionizing radiation curableresin composition is cross-linked and cured by being irradiated withultraviolet rays or electron beams. Additionally, electromagneticradiation including X rays and γ rays and charged particle radiationincluding a rays and ion lines can be used as ionizing radiation.

In the first embodiment of the invention, a polycarbonate(meth)acrylate(A) and a multi-functional (meth)acrylate (B) are at least used as theionizing radiation curable resin. If the mass ratio (A)/(B) of thepolycarbonate(meth)acrylate (A) to the multi-functional (meth)acrylate(B) is more than 98/2 (specifically if the amount of thepolycarbonate(meth)acrylate (A) is more than 98 mass %), the scratchresistance decreases. On the other hand, if the mass ratio (A)/(B) ofthe polycarbonate(meth)acrylate (A) to the multi-functional(meth)acrylate (B) is less than 70/30 (specifically if the amount of thepolycarbonate(meth)acrylate (A) is less than 70 mass %), thethree-dimensional formability decreases. Preferably, the mass ratio(A)/(B) of the polycarbonate(meth)acrylate (A) to the multi-functional(meth)acrylate (B) is (95/5)-(80/20).

In the present invention, “(meth)acrylate” means “acrylate ormethacrylate.” Other similar terms are also regarded as synonymous inthis way.

The polycarbonate(meth)acrylate (A) used in the present invention islimited in particular as long as having a carbonate bond in the polymermain chain and further having a (meth)acrylate at the end or the sidechain. This polycarbonate(meth)acrylate has preferably more than twofunctional groups from the viewpoint of cross-linking and curing.

The above-mentioned polycarbonate(meth)acrylate (A) is obtained, forexample, by converting a part or all of the hydroxyl groups of apolycarbonate polyol to a (meth)acrylate (acrylic ester or methacrylicester). This esterification can be conducted by a typically usedesterification. For example, this esterification is conducted by 1)condensing a polycarbonate polyol together with an acrylic acid halideor a methacrylic acid halide in the presence of a base; 2) condensing apolycarbonate polyol together with an acrylic acid anhydride or amethacrylic acid anhydride in the presence of a catalyst; or 3)condensing a polycarbonate polyol together with acrylic acid ormethacrylic acid in the presence of an acid catalyst.

The above-mentioned polycarbonate polyol has a carbonate bond in thepolymer main chain and further has 2 or more, preferably 2-50, morepreferably 3-50 hydroxyl groups at the end or the side chain. A typicalmethod of generating this polycarbonate polyol is the polycondensationreaction of a diol compound (d), a trivalent or higher polyvalentalcohol (e), and a compound (f) to be the carbonyl component.

The diol compound (d) used as the raw material is represented by thegeneral formula HO—R¹—OH. R¹ is a divalent hydrocarbon group with 2-20atoms and may include an ether bond. For example, R¹ is a normal orbranched alkylene group, a cyclohexylene group, and a phenylene group.

The specific example of the diol compound includes ethylene glycol,1,2-propylene glycol, diethylene glycol, dipropylene glycol, triethyleneglycol, polyethylene glycol, neopentyl glycol, 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5 pentanediol,1,6-hexanediol, 1,8-octanediol, 1,3-bis(2-hydroxyethoxy)benzene,1,4-bis(2-hydroxyethoxy)benzene, neopentyl glycol, 1,4-cyclohexanediol,and 1,4-cyclohexanedimethanol. These diols may be used alone or incombination with two or more kinds.

The example of the polyvalent alcohol (e) includes trimethylolpropane,trimethylolethane, pentaerythritol, ditrimethylolpropane,dipentaerythritol, glycerin, and sorbitol. The trivalent or higherpolyvalent alcohol (e) may have a hydroxyl group in which ethyleneoxide, propylene oxide, or other alkylene oxides are added in anequivalent of 1-5 based on the hydroxyl groups of each of thesepolyvalent alcohols. These polyvalent alcohols may be used alone or incombination with two or more kinds.

The compound (f) to be the carbonyl component is any one selected fromdiester carbonate, phosgene, and these equivalents of thereof.Specifically, the compound (f) includes diester carbonates such asdimethyl carbonate, diethyl carbonate, diisopropyl carbonate, diphenylcarbonate, ethylene carbonate, and propylene carbonate; phosgene; orhalogenated formates such as methyl chloroformate, ethyl chloroformate,and phenyl chloroformate. These may be used alone or in combination withtwo or more kinds.

The polycarbonate polyol is synthesized by the polycondensation reactionof the above-mentioned diol compound (d), trivalent or higher polyvalentalcohol (e), and compound (f) to be the carbonyl component under ageneral condition. For example, the molar ratio (d)/(e) of the diolcompound (d) to the polyvalent alcohol (e) as raw materials preferablyfalls within the range of (50/50)-(99/1). The molar ratio of thecompound (f) to be the carbonyl component to the diol compound (d) andthe polyvalent alcohol (e) is preferably 0.2-2 equivalents based on thehydroxyl groups of the diol compound and the polyvalent alcohol.

The equivalent number (eq./mol) of the hydroxyl groups existing in thepolycarbonate polyol after the condensation polymerization conducted atthe above-mentioned molar ratio is 3 or more, preferably 3-50, morepreferably 3-20 on average in one molecule. This range generates therequired number of the (meth)acrylate groups by the below-mentionedesterification and provides moderate flexibility to apolycarbonate(meth)acrylate resin. The terminal functional groups ofthis polycarbonate polyol are usually OH groups, but some of which maybe carbonate groups.

The method of generating the polycarbonate polyol is described in, forexample, JP S64-1726 A. This polycarbonate polyol can also be producedby the transesterification of a polycarbonate diol and a trivalent orhigher polyvalent alcohol as described in JP H3-181517 A.

The molecular weight of the polycarbonate(meth)acrylate (A) used in thepresent invention is measured by GPC analysis. The standard polystyreneequivalent weight-average molecular weight is preferably 500 or more,more preferably 1,000 or more, further more preferably more than 2,000.The upper limit of the weight-average molecular weight of thepolycarbonate(meth)acrylate (A) is not limited in particular, butpreferably 100,000 or less, more preferably 50,000 or less from theviewpoint of controlling the viscosity not to be increased too much.From the viewpoint of maintaining the scratch resistance as well as thethree-dimensional formability, the upper limit of the weight-averagemolecular weight of the polycarbonate(meth)acrylate (A) is further morepreferably more than 2,000 and 50,000 or less, particularly preferably5,000-20,000.

The multi-functional (meth)acrylate (B) used in the present invention isnot limited in particular as long as being a (meth)acrylate with two ormore functional groups. However, a (meth)acrylate with three or morefunctional groups is preferable from the viewpoint of the curability.The n functional groups means herein that the number of ethyleneunsaturated bonds {(meth)acryloyl groups} in a molecule is n.

The multi-functional (meth)acrylate (B) may be an oligomer or a monomer.However, the multi-functional (meth)acrylate (B) is preferably amulti-functional (meth)acrylate oligomer from the viewpoint of improvingthe three-dimensional formability.

The above-mentioned multi-functional (meth)acrylate oligomer includes,for example, a urethane (meth)acrylate oligomer, an epoxy (meth)acrylateoligomer, a polyester (meth)acrylate oligomer, and a polyether(meth)acrylate oligomer. The urethane (meth)acrylate oligomer can beobtained, for example, by esterifying a (meth)acrylic acid with apolyurethane oligomer obtained by reacting a polyetherpolyol or apolyester polyol with a polyisocyanate. The epoxy (meth)acrylateoligomer can be obtained, for example, by esterifying a (meth)acrylicacid with the oxirane ring of a bisphenol epoxy resin or a novolac epoxyresin with a relatively low molecular weight. A carboxyl modified-epoxy(meth)acrylate oligomer obtained by partially modifying this epoxy(meth)acrylate oligomer with a dibasic carboxylic acid anhydride can beused. The polyester (meth)acrylate oligomer can be obtained, forexample, by esterifying a (meth)acrylic acid with the hydroxyl groups ofa polyester oligomer having hydroxyl groups at the both ends that hasbeing obtained by condensing a polyvalent carboxylic acid with apolyvalent alcohol or by esterifying a (meth)acrylic acid with thehydroxyl group at an end of an oligomer obtained by adding an alkyleneoxide to a polyvalent carboxylic acid. The polyether (meth)acrylateoligomer can be obtained by esterifying a (meth)acrylic acid with thehydroxyl groups of a polyetherpolyol.

Other multi-functional (meth)acrylate oligomers include a highhydrophobic polybutadiene (meth)acrylate oligomer with a (meth)acrylategroup in the side chain of the polybutadiene oligomer; a silicone(meth)acrylate oligomer with a polysiloxane bond in the main chain; andan aminoplast resin (meth)acrylate oligomer in which an aminoplast resinwith a large number of reactive groups in the small molecular ismodified.

The above-mentioned multi-functional (meth)acrylate monomer includes,specifically, ethylene glycol di(meth)acrylate, propylene glycoldi(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycoldi(meth)acrylate, hydroxy pivalic acid neopentyl glycoldi(meth)acrylate, dicyclopentanyl di(meth)acrylate,caprolactone-modified dicyclopentenyl di(meth)acrylate, ethyleneoxide-modified phosphoric acid di(meth)acrylate, allylated cyclohexyldi(meth)acrylate, isocyanurate di(meth)acrylate, trimethylolpropanetri(meth)acrylate, ethylene oxide-modified trimethylolpropanetri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionicacid-modified dipentaerythritol tri(meth)acrylate, pentaerythritoltri(meth)acrylate, propylene oxide-modified trimethylolpropanetri(meth)acrylate, tris(acryloxyethyl) isocyanurate, propionicacid-modified dipentaerythritol penta(meth)acrylate, dipentaerythritolhexa(meth)acrylate, ethylene oxide-modified dipentaerythritolhexa(meth)acrylate, and caprolactone-modified dipentaerythritolhexa(meth)acrylate.

The above-mentioned multi-functional (meth)acrylate oligomers andmonomers may be used alone or in combination of two or more kinds.

The second embodiment of the invention is a decorative sheet includingat least a surface protective layer on a substrate, in which the surfaceprotective layer includes a cured material of an ionizing radiationcurable resin composition at least containing an acrylic silicone(meth)acrylate (C) and a multi-functional (meth)acrylate (B) in a massratio (C)/(B) of (50/50)-(95/5). The ionizing radiation curable resincomposition, the ionizing radiation curable resin, and the ionizingradiation are as described above.

In the second embodiment of the invention, an acrylic silicone(meth)acrylate (C) and a multi-functional (meth)acrylate (B) are atleast used as the ionizing radiation curable resin. If the mass ratio(C)/(B) is less than (50/50) (specifically if the amount of (C) is lessthan 50 mass % based on the total amount of (B) and (C)), the chemicalresistance and the scratch resistance decrease. On the other hand, ifthe mass ratio (C)/(B) is more than (95/5) (specifically if the amountof (C) is more than 95 mass % based on the total amount of (B) and (C)),the scratch resistance and the three-dimensional formability decrease.

The acrylic silicone (meth)acrylate (C) used in the present invention isnot limited in particular as long as a part of the structure of theacrylic resin is substituted with a siloxane bond (Si—O) in one moleculeand as long as the side chain and/or the main chain end of the acrylicresin has two or more (meth)acryloyloxy (acryloyloxy or methacryloyloxy)groups as functional groups in one molecule.

The example of this acrylic silicone (meth)acrylate (C) preferablyincludes the structure of an acrylic resin with a siloxane bond at theside chain as disclosed in JP 2007-070544 A.

The acrylic silicone (meth)acrylate (C) used in the present inventioncan be synthesized, for example, by the radical copolymerization of asilicone macromonomer with a (meth)acrylate monomer in the existence ofa radical polymerization initiator.

The (meth)acrylate monomer includes methyl(meth)acrylate,ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate,2-ethylhexyl(meth)acrylate, and glycidyl(meth)acrylate. These(meth)acrylate monomers are used alone or in combination with two kinds.

The silicone macromonomer is synthesized, for example, by the anionicliving polymerization of a hexa-alkyl cyclotrisiloxane in the existenceof n-butyl lithium or lithium silanolate as the polymerization initiatorand then by capping reaction with a silane containing a radicallypolymerizable unsaturated group. As the silicone macromonomer, thecompound represented by the following formula (1) is suitably used.

In the formula (1), R¹ represents an alkyl group with 1-4 carbon atoms,preferably a methyl group or an n-butyl group. R² represents amonovalent organic group, preferably —CH═CH₂, —C₆H₄—CH═CH₂,—(CH₂)₃O(CO)CH═CH₂, or —(CH₂)₃O(CO)C(CH₃)═CH₂. R³s may be the same as ordifferent from each other, each of which represents a hydrocarbon groupwith 1-6 carbon atoms, preferably an alkyl group or a phenyl group with1-4 carbon atoms, more preferably a methyl group. The value n is notlimited in particular, but the number-average molecular weight of thesilicone macromonomer is preferably 1000-30000, more preferably1,000-20,000.

For example, the acrylic silicone (meth)acrylate (C) obtained by usingthe above-mentioned raw materials has the following structural unitsrepresented by the formulas (2), (3), and (4).

In the formulas (2), (3), and (4), R¹ and R³ represent the same asdefined in the formula (1). R⁴ represents a hydrogen atom or a methylgroup. R⁵ represents an alkyl group or a glycidyl group in theabove-mentioned (meth)acrylate monomer or represents an alkyl group thatmay have a functional group such as an alkyl group or a glycidyl groupin the above-mentioned (meth)acrylate monomer. R⁶ represents an organicgroup with a (meth)acryloyloxy group.

The above-mentioned acrylic silicone (meth)acrylates (C) are used aloneor in combination with two kinds.

The molecular weight of the above-mentioned acrylic silicone(meth)acrylate (C) is measured by GPC analysis. The standard polystyreneequivalent weight-average molecular weight is preferably 1,000 or more,more preferably 2,000 or more. The upper limit of the weight-averagemolecular weight of the acrylic silicone (meth)acrylate (C) is notlimited in particular, but preferably 150,000 or less, more preferably100,000 or less from the viewpoint of controlling the viscosity not tobe increased too much. From the viewpoint of maintaining thethree-dimensional formability, the chemical resistance, and the scratchresistance, the upper limit of the weight-average molecular weight isfurther more preferably 2,000-100,000.

The mean molecular weight between the cross-linking points of theacrylic silicone (meth)acrylate (C) is preferably 100-2,500. The meanmolecular weight between the cross-linking points is preferably 100 ormore from the viewpoint of the three-dimensional formability and alsopreferably 2,500 or less from the viewpoint of the chemical resistanceand the scratch resistance.

The multi-functional (meth)acrylate (B) used in the second embodiment ofthe invention is the same as that used in the first embodiment. Inparticular, in the second embodiment of the present invention, theYoung's modulus determined in the below-mentioned test preferably60-2,000 MPa, more preferably 100-1,500 MPa from the viewpoint ofmaintaining the three-dimensional formability and the scratchresistance.

In the present invention, a monofunctional (meth)acrylate can beoptionally used together with the above-mentioned polyfunctional(meth)acrylate (B) for the purpose of decreasing the viscosity withoutdeparting from the scope of the present invention. The monofunctional(meth)acrylate includes, for example, methyl(meth)acrylate,ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate,pentyl(meth)acrylate, hexyl(meth)acrylate, cyclohexyl(meth)acrylate,2-ethylhexyl(meth)acrylate, lauryl(meth)acrylate, stearyl(meth)acrylate,and isobornyl(meth)acrylate. These monofunctional (meth)acrylates may beused alone or in combination of two or more kinds.

When an ultraviolet curable resin composition is used as the ionizingradiation curable resin composition, a photopolymerization initiator ispreferably added in a content of about 0.1-5 parts by mass based on 100parts by mass of the ultraviolet curable resin. The photopolymerizationinitiator can be optionally selected from conventionally used oneswithout particular limitation, including, for example, benzoin, benzoinmethyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoinn-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone,2,2-diethoxy-2-phenylacetophenone,2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexyl phenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one,4-(2-hydroxyethoxyl)phenyl-2(hydroxy-2-propyl)ketone, benzophenone,p-phenylbenzophenone, 4,4′-diethylaminobenzophenone,dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone,2-tertiary-butylanthraquinone, 2-aminoanthraquinone,2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone,2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethylketal,and acetophenone dimethyl ketal.

For example, a photosensitizer based on a p-dimethylbenzoic acid ester,a tertiary amine, a thiol, or the like can be used.

In the present invention, an electron beam curable resin composition ispreferably used as the ionizing radiation curable resin composition. Theelectron beam curable resin composition is allowed to be solventless andpreferred from the viewpoint of environment and health. Furthermore, theelectron beam curable resin composition provides stable curingcharacteristics without a photopolymerization initiator.

In the ionizing radiation curable resin composition forming the surfaceprotective layer in the present invention, various additives can bemixed according to the desired physical properties of a curable resinlayer to be obtained. These additives include, for example, a weatherresistance improver, an abrasion resistance enhancer, a polymerizationinhibitor, a cross-linking agent, an infrared absorbent, an antistaticagent, an adhesion enhancer, a leveling agent, a thixotropic agent, acoupling agent, a plasticizer, an antifoaming agent, a filler, asolvent, and a colorant.

As the weather resistance improver, an ultraviolet absorber, and aphotostabilizer can be used. The ultraviolet absorber may be inorganicor organic. As the inorganic ultraviolet absorber, titanium dioxide,cerium oxide, and zinc oxide, which have a mean particle size of about5-120 nm, can preferably be used. The organic ultraviolet absorber isbased on, for example, a benzotriazole, specifically2-(2-hydroxy-5-methylphenyl)benzotriazole,2-(2-hydroxy-3,5-di-tert-amylphenyl)benzotriazole, and3-[3-(benzotriazole-2-yl)-5-tert-butyl-4-hydroxyphenyl]propionate esterof polyethylene glycol, or the like. The photostabilizer includes, forexample, a photostabilizer based on a hindered amine, specificallybis(1,2,2,6,6-pentamethyl-4-piperidyl)2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2′-n-butylmalonate,bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate,tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, or the like. Furthermore, a reactive ultravioletabsorber and a reactive photostabilizer that have a polymerizable groupsuch as a (meth)acryloyl group in the molecule can be used. Theultraviolet absorber and the photostabilizer that are to be used can becopolymerized without impairing the properties (scratch resistance andthree-dimensional formability) as the surface protective layerconsisting of the polymer according to the present invention.

The abrasion resistance enhancer includes, for example, sphericalparticles of inorganic substances such as α-alumina, silica, kaolinite,iron oxide, diamond, and silicon carbide. The shape of particle includesa sphere, an ellipsoid, a polyhedron, a scale, and the like, preferablya sphere but is not limited in particular. The particles of organicsubstances include beads consisting of a synthetic resin such as across-linked acrylic resin and a polycarbonate resin. The particle sizeis typically about 30-200% of the film thickness. Particularly,spherical α-alumina is preferable in terms of high hardness, largeeffect on the improvement of the abrasion resistance, and easyobtainability of the spherical particles.

As the polymerization inhibitor, for example, hydroquinone,p-benzoquinone, hydroquinone monomethyl ether, pyrogallol,t-butylcatechol, and the like are used.

As the cross-linking agent, for example, a polyisocyanate compound, anepoxy compound, a metal chelate compound, an aziridine compound, anoxazoline compound, and the like are used.

As the filler, for example, barium sulfate, talc, clay, calciumcarbonate, aluminium hydroxide, and the like are used.

As the colorant, for example, well-known color pigments such asquinacridone red, isoindolinone yellow, phthalocyanine blue,phthalocyanine green, titanium oxide, and carbon black, and the like areused.

As the infrared absorbent, for example, a dithiol metal complex, aphthalocyanine compound, a diimmonium compound, and the like are used.

The configuration of the decorative sheet of the present invention willbe explained in detail in reference to FIG. 1.

FIG. 1 shows a pattern diagram illustrating the cross section of anaspect of the decorative sheet 10 of the present invention used forinsert molding. In the example shown in FIG. 1, a picture layer 12, aprimer layer 13, and a surface protective layer 14 are sequentiallylaminated on a substrate 11. The surface protective layer 14 is formedby cross-linking and curing the above-mentioned ionizing radiationcurable resin composition.

The substrate 11 is selected in consideration of the vacuum formability,and a resin sheet consisting of a thermoplastic resin is thereforetypically used. As the thermoplastic resin, polyolefin resins such as anacrylonitrile-butadiene-styrene resin (hereinafter referred to as “ABSresin”), an acrylic resin, a polypropylene, and a polyethylene; apolycarbonate resin; a vinyl chloride resin, and the like are generallyused. For the substrate 11, a single-layer sheet of these resins or amultilayer sheet of the same or different resins can be used.

The thickness of the substrate is selected based on the application,typically about 0.05-1.0 mm, more typically about 0.1-0.7 mm inconsideration of the cost and the like.

These substrates can be subjected to physical or chemical surfacetreatment by oxidation, unleveling, or the like to improve the adhesionto the layer provided on the sheet, if desired.

The oxidation includes, for example, the corona discharge treatment,chromium oxidation treatment, flame treatment, hot air treatment, andultraviolet-ozone treatment. The unleveling includes, for example,sandblasting and solvent treatment. These surface treatments areoptionally selected depending on the type of substrate. Generally,corona discharge treatment is preferably used from the viewpoint of theeffect, the operability, and the like.

On the substrate, a primer layer may be formed, painting may be appliedfor adjusting the color, or a designed pattern may previously be formed.

The picture layer 12 shown in FIG. 1 provides decoration to a decorativeresin-molded article. The picture layer is formed by printing variouspatterns with ink and a printer. The pattern includes a wood grainpattern, a pebble grain pattern imitating the surface of rock, such asmarble (for example, travertine marble), a texture grain patternimitating texture and cloth, a tiling pattern, and a brickwork pattern,as well as a mosaic and a patchwork patterns made by fitting togetherthese patterns. These patterns are formed by process printing usingtypical process colors: yellow, red, blue, and black. These patterns arealso each formed by process printing characterized by preparing printingplates corresponding to the colors-composing these respective patterns.

As the design ink used for the picture layer 12, colorants such as apigment and a dye, an extender pigment, a solvent, a stabilizer, aplasticizer, a catalyst, and a hardener, which are optionally mixed in abinder, are used. The binder is used without limitation in particular.For example, a polyurethane resin, a vinyl chloride/vinyl acetatecopolymer resin, a vinyl chloride/vinyl acetate/acrylic copolymer resin,a chlorinated polypropylene resin, an acrylic resin, a polyester resin,a polyamide resin, a butyral resin, a polystyrene resin, anitrocellulose resin, a cellulose acetate resin, and the like areoptionally used alone or in combination with two or more kinds.

As the colorant, inorganic pigments such as carbon black (Indian ink),iron black, titanium white, antimony white, chrome yellow, titaniumyellow, red iron oxide, cadmium red, ultramarine blue, and cobalt blue;organic pigments or dyes such as quinacridone red, isoindolinone yellow,and phthalocyanine blue; a metallic pigment consisting of scale-likefoil of aluminum, brass, or the like; a pearlescent (pearl) pigmentconsisting of scale-like foil of titanium dioxide-coated mica, basiclead carbonate, or the like; and the like are used.

The decorative sheet 10 of the present invention may be provided with ahiding layer (not shown) between the substrate 11 and the picture layer12, if desired. The hiding layer is provided so as to avoid the colorchange or variation of the surface of the substrate 11 from affectingthe color of the pattern of the decorative sheet 10. The hiding layer isoften formed in an opaque color. A so-called solid print layer with athickness of 1-20 μm is suitably used for the hiding layer.

To hardly cause a minute crack and whitening on the drawn part of thesurface protective layer 14, the decorative sheet 10 of the presentinvention can be provided with the primer layer 13 between the picturelayer 12 and the surface protective layer 14, if desired. As the primercomposition forming the primer layer 13, binder resins such as a(meth)acrylic resin, a urethane resin, a (meth)acrylic-urethanecopolymer resin, a vinyl chloride-vinyl acetate copolymer, a polyesterresin, a butyral resin, a chlorinated polypropylene, and a chlorinatedpolyethylene are preferably used alone or in combination with two ormore kinds. Among these, a urethane resin, a (meth)acrylic resin, and a(meth)acrylic/urethane copolymer resin are preferable. From theviewpoint of the chemical resistance and the adhesion to the surfaceprotective layer 14, a cross-linking agent is preferably used for theformation of the primer layer 14.

The (meth)acrylic resin includes a homopolymer of (meth)acrylic acidester, a copolymer of two or more different kinds of (meth)acrylic acidester monomers, and a copolymer of a (meth)acrylic acid ester monomerand other monomers. Specifically, a (meth)acrylic resin consisting of ahomopolymer or a copolymer containing a (meth)acrylic acid ester, suchas poly[methyl(meth)acrylate], poly[ethyl(meth)acrylate],poly[propyl(meth)acrylate], poly[butyl(meth)acrylate],methyl(meth)acrylate-butyl (meth)acrylate copolymer,ethyl(meth)acrylate-butyl (meth)acrylate copolymer,ethylene-methyl(meth)acrylate copolymer, or styrene-methyl(meth)acrylatecopolymer, is suitably used. The (meth)acryl means acryl or methacrylherein.

As the urethane resin, a polyurethane consisting of polyol (polyvalentalcohol) as the base compound and isocyanate as the cross-linking agent(curing agent) can be used. The polyol has two or more hydroxyl groupsin the molecule. For example, a polyester polyol, a polyethylene glycol,a polypropylene glycol, an acrylic polyol, a polyether polyol, and thelike are used. As the above-mentioned isocyanate, a polyvalentisocyanate with two or more isocyanate groups in the molecule; anaromatic isocyanate such as 4,4-diphenylmethane diisocyanate; andaliphatic (or alicyclic) isocyanates such as hexamethylene diisocyanate,isophorone diisocyanate, hydrogenated tolylene diisocyanate, andhydrogenated diphenylmethane diisocyanate are used. The urethane resincan be combined with a butyral resin.

From the viewpoint of the adhesion to the surface protective layer 14,the physical properties, and the formability after cross-linking, anacrylic polyol or a polyester polyol as the polyol is preferablycombined with hexamethylene diisocyanate or 4,4-diphenylmethanediisocyanate as the cross-linking agent. Particularly, an acrylic polyolis preferably combined with hexamethylene diisocyanate.

The (meth)acrylic-urethane copolymer resin is preferably, for example,an acrylic/urethane (polyester urethane) block copolymer resin. As thecuring agent, the above-mentioned various isocyanates are used. In theacrylic/urethane (polyester urethane) block copolymer resin, the ratio(mass ratio) of acryl/urethane is preferably adjusted to (9/1)-(1/9),more preferably (8/2)-(2/8), if desired. Since it can be used forvarious decorative sheets, this acrylic/urethane (polyester urethane)block copolymer resin is particularly preferable as the resin used forthe primer composition.

To improve the adhesion to the injection resin, the decorative sheet 10of the present invention can be provided with aback surface (opposite tothe surface protective layer 14) adhesive layer (not shown) of thedecorative sheet 10, if desired. For the adhesive layer, a thermoplasticresin or a curable resin is used according to the injection resin. Thethermoplastic resin includes an acrylic resin, an acrylic modifiedpolyolefin resin, a chlorinated polyolefin resin, a vinyl chloride-vinylacetate copolymer, a thermoplastic urethane resin, a thermoplasticpolyester resin, a polyamide resin, and a rubber-based resin. These canbe used alone or in combination with two or more kinds. Thethermosetting resin includes a urethane resin and an epoxy resin.

The surface protective layer 14 is formed by preparing, applying,cross-linking, and curing a coating liquid containing theabove-mentioned ionizing radiation curable resin composition. Theviscosity of the coating liquid is not limited in particular as long asbeing capable of forming an uncured resin layer on the surface of thesubstrate by the below-mentioned coating method.

In the present invention, a prepared coating liquid is coated on thesurface of the picture layer 12 or the primer layer 13 by well-knownmethods such as gravure coating, bar coating, roll coating, reverse rollcoating, and comma coating, preferably gravure coating to form theuncured resin layer so that the surface protective layer 14 a thicknessof 1-1000 μm after curing.

In the present invention, the uncured resin layer formed in this way iscured by being irradiated with ionizing radiation such as electron beamsor ultraviolet rays. When electron beams are used as the ionizingradiation, the accelerating voltage can appropriately be selected basedon the resin to be used and the thickness of the layer. However, theuncured resin layer is typically preferably cured at an acceleratingvoltage of about 70-300 kV.

In the irradiation with electron beams, the higher accelerating voltageincreases the penetrating power more. When a substrate deteriorated byelectron beams is used as the substrate 11, the accelerating voltage isselected so that the penetration depth of electron beams issubstantially equal to the thickness of the resin layer. Therefore, thesubstrate 11 can be prevented from being excessively irradiated withelectron beams to minimize the deterioration of the substrate beingcaused by excess electron beams.

The irradiation dose when the crosslink density of the resin compositionlayer is saturated is preferable, which is selected from the range oftypically 5-300 kGy (0.5-30 Mrad), preferably 10-50 kGy (1-5 Mrad).

The electron beam source is not limited in particular. For example,various electron beam accelerators such as a Cockcroft-Waltonaccelerator, a van de Graaff accelerator, a resonance transformeraccelerator, an insulated core transformer accelerator, a linearaccelerator, a dynamitron accelerator, and a high frequency acceleratorcan be used.

When used as ionizing radiation, the ultraviolet rays are emitted at awavelength of 190-380 nm. The ultraviolet ray source is not limited inparticular. For example, a high-pressure mercury lamp, a low-pressuremercury lamp, a metal halide lamp, and a carbon-arc lamp are used.

To the cured resin layer formed in this way, various additives are addedto provide various functions, for example, with high hardness andscratch resistance, such as hard coating function, antifog coatingfunction, antifouling coating function, anti-glare coating function,antireflection coating function, ultraviolet screen coating function,and infrared screen coating function.

In the present invention, the surface protective layer 14 preferably hasa thickness of 1-1000 μm. The surface protective layer 14 with athickness of 1 μm or more after curing obtains sufficient physicalproperties such as the scratch resistance and the weatherability as aprotection layer. On the other hand, the surface protective layer 14with a thickness of 1000 μm or less 1 after curing has an economicaladvantage because it is uniformly cured by easily uniformly beingirradiated with ionizing radiation.

The surface protective layer 14 with a thickness of preferably 1-50 μm,more preferably 1-30 μm can improve the three-dimensional formability toobtain high shape following capability to a complex three dimensionalshape for use in an automotive interior and the like. Therefore, thedecorative sheet of the present invention can exhibit excellentthree-dimensional formability even if a hard ionizing radiation curableresin is combined. Furthermore, the decorative sheet can harden thecoating film without impairing the three-dimensional formability. As theresult, the decorative sheet can have a preferably excellent scratchresistance in the processing and the practical use.

Even if the surface protective layer 14 is thicker than the conventionalones, the decorative sheet of the present invention obtains sufficientlyhigh three-dimensional formability. Therefore, the decorative sheet isuseful for a member required to have a high film thickness on thesurface protective layer, particularly for an automotive exterior.

The picture layer 12 is formed by a typical printing method such asgravure printing. The hiding layer is formed by a typical printingmethod such as gravure printing; and typical coating methods such asgravure coating, gravure reverse coating, gravure offset coating,spinner coating, roll coating, and reverse roll coating.

The primer layer 13 and the adhesive layer are formed by typical coatingmethods and transcription coating methods such as gravure coating,gravure reverse coating, gravure offset coating, spinner coating, rollcoating, reverse roll coating, kiss coating, wheeler coating, dipcoating, solid coating by silk screen, wire bar coating, flow coating,comma coating, continuous flow coating, brush coating, and spraycoating. In the transfer coating, the coating film of the primer layer13 or the adhesive layer is formed on a thin sheet (film substrate) andthen coated on the surface of a target layer of the decorative sheet 10.

The thickness of the picture layer 12 is appropriately selected by thedesign. The thickness of the hiding layer is about 1-20 μm.

The thickness of the primer layer 13 is preferably about 0.1-10 μm. Theprimer layer with a thickness of 0.1 μm or more can substantiallyproduces an effect to preventing a crack, breaking, whitening, and thelike from being generated on the surface protective layer. On the otherhand, the primer layer with a thickness of 10 μm or less does preferablynot fluctuate the three-dimensional formability because the coated filmis stably dried and cured when the primer layer is coated. Therefore,the thickness of the primer layer is more preferably about 1-10 μm. Forthe same reason as the primer layer, the thickness of the adhesive layeris preferably about 0.1-10 μm.

The decorative sheet of the present invention can be used for variousinjection molding processes such as insert molding, simultaneousinjection-molding and decoration, blow molding, and gas injectionmolding. The decorative sheet is suitably used for insert molding andsimultaneous injection-molding and decoration.

In the insert molding, the decorative sheet of the present invention issubjected to previously vacuum forming (off-line preforming) to form thesurface shape of a molded article with a vacuum forming mold. Then, thedecorative sheet with the surface shape is trimmed to obtain a moldedsheet. This molded sheet is inserted in an injection mold, and theinjection mold is clamped. Then, a fluid state of resin is injected andsolidified in the mold. The decorative sheet is integrated with theouter surface of the formed resin composite at the same time ofinjection molding to produce a decorative resin-molded article.

The injection resin, typically polyolefin resins such as polyethyleneand polypropylene; and thermoplastic resins such as an ABS resin, astyrene resin, a polycarbonate resin, an acrylic resin, and a vinylchloride resin are used based on the application. Thermosetting resinssuch as a urethane resin and an epoxy resin can be used based on theapplication.

In the simultaneous injection-molding and decoration, the decorativesheet of the present invention is disposed on a female mold convertibleto a vacuum forming mold in which a vacuum hole for injection molding isprovided. This female mold is used for preforming (in-line preforming),and then the injection mold is clamped. Then, a fluid state of resin isinjected, filled, and solidified in the mold. The decorative sheet isintegrated with the outer surface of the formed resin composite at thesame time of injection molding to produce a decorative resin-moldedarticle.

In the simultaneous injection-molding and decoration, the decorativesheet may receive a thermal pressure from the injected resin. When thedecorative sheet, the drawing of which is small, is near the flat plate,the decorative sheet may not be preheated. In the simultaneousinjection-molding and decoration, the injection resin as explained inthe description on the insert molding can be used.

With no cracks being generated on the surface protective layer duringthe molding process, the decorating resin compact produced as describedabove has excellent three-dimensional formability, and the surface hashigh scratch resistance. The decorating resin compact also has highsolvent resistance and chemical resistance. In the manufacturing methodof the present invention, the surface protective layer is completelycured at the stage of producing the decorative sheet. Therefore, thestep of cross-linking and curing the surface protective layer isunnecessary after the decorating resin compact is produced.

EXAMPLES

The present invention will be explained in more detail with reference toExamples below but is not limited thereto.

Evaluation Method (1) Three-Dimensional Formability (Vacuum Forming)

The decorative sheet obtained in each of the examples and thecomparative examples is subjected to vacuum forming in thebelow-mentioned methods, and then the appearance was evaluated. Thecriterion is as follows.

AAA: No coating cracks nor whitening was observed on the surfaceprotective layer, and good shape following to the mold was accomplished.

AA: A minute coating crack or whitening was observed on a part of thethree-dimensional part or the fully drawn part, but no practicalproblems were identified.

A: A minor coating crack or whitening was observed on a part of thethree-dimensional part or the fully drawn part.

F: No shape following to the mold was able to be accomplished, and acoating crack and whitening were observed on the surface protectivelayer.

Vacuum Forming

The decorative sheet is heated and softened at 160° C. with an infraredheater. The decorative sheet is subjected to vacuum forming at a maximumdraw ratio of 150% by using a vacuum forming mold and formed in theinner shape of the mold. The decorative sheet is cooled and thendemolded.

(2) Scratch Resistance (Method A)

The appearance of the test specimen was evaluated after scratched 5times at a load of 1.5 kgf with #0000 steel wool. The criterion is asfollows.

AAA: No flaws were observed.

AA: A minute flaw was observed on the surface. But no coating crack norwhitening was observed on the surface.

A: A minor flaw was observed on the surface.

F: A significant flaw was observed on the surface.

(3) Scratch Resistance (Method B)

A color fastness rubbing tester available from TESTER SANGYO CO., LTD.was used. The appearance of the test specimen was evaluated afterscratched 1,000 times at a load of 500 gf with JIS test fabric-cotton(Canequim #3) as white cotton fabric for rubbing. The criterion is asfollows.

AAA: Very few flaws were observed.

AA: A minute flaw was observed on the surface. But no coating crack norwhitening was observed on the surface.

A: A minor flaw was observed on the surface.

F: A significant flaw was generated together with a coating crack orwhitening on the entire surface.

(4) Chemical Resistance

Ethanol was added dropwise to the surface protective layer of thedecorative sheet obtained in each of the examples and the comparativeexamples. The dropwisely added part was covered with a watch glass andleft at room temperature (25° C.) for 1 hour. The watch glass wasremoved, and then the appearance was observed and evaluated based on thefollowing criterion.

AA: No significant changes were observed on the coated film.

F: The coated film was swollen or detached.

(5) Weight-Average Molecular Weight and Number-Average Molecular Weight

A high speed GPC available from TOSOH CORPORATION was used. The columnused is also available from TOSOH CORPORATION, the brand name of whichis “TSKgel αM.” As the solvent, N-methyl-2-pyrrolidinone (NMP) was used.The measurement was conducted at a temperature of 40° C. and a flow rateof 0.5 cc/min. The weight-average molecular weight and thenumber-average molecular weight in the present invention were convertedinto standard polystyrene equivalents.

(6) Mean Molecular Weight Between Cross-Linking Points

The mean molecular weight between the cross-linking points wascalculated by dividing the number-average molecular weight obtainedabove by the number of functional groups.

(7) Young's Modulus

The tension test in accordance with JIS K 7127 was conducted. Then, theYoung's modulus was determined by the following equation based on thetension when a load was applied to the test specimen of the curedcoating film of a multi-functional (meth)acrylate.

E=(W×L)/(A×Δt)

In the equation, W represents a load (kg), L represents a baseline gaugelength (cm), A represents a cross-sectional area of the test specimen,and Δt represents a gauge length (cm) at a load W.

The resin composition produced in each of the examples and thecomparative examples was applied on a polyethylene terephthalate(hereinafter referred to as “PET”) film to which surface treatment wasnot applied so that the film thickness after the cross-linking andcuring is about 15 μm. This uncured resin layer was irradiated withelectron beams with an irradiation dose of 50 kGy (5 Mrad) at anaccelerating voltage of 165 kV to cure the electron beam curable resincomposition. The cured film was peeled off from the PET film, and then atest specimen was cut in a width of 25 mm and a length of 120 mm out ofthe cured film.

The testing condition included a tension rate of 50 mm/minute, aninterchuck distance of 80 mm, and a gauge length of 50 mm.

Examples 1-7 and Comparative Examples 1-4

As the substrate, an ABS resin film (flexural modulus; 2000 MPa,thickness; 400 μm) was used to form a picture layer with a wood grainpattern on the surface of the film by gravure printing using acrylicresin inks. Then, a primer layer consisting of a primer compositioncontaining an acrylic polyol and hexamethylene diisocyanate was coatedon the surface of the picture layer by gravure reverse coating. (Thehexamethylene diisocyanate was mixed in the same NCO equivalent as theOH equivalent of the acrylic polyol). The thickness of the primer layerwas 3 μm.

Then, the electron beam curable resin composition shown in Table 1 wascoated on the surface of the primer layer by gravure coating so that thethickness (μm) of the resin composition after curing was as described inTable 1. This uncured resin layer was irradiated with electron beamswith an irradiation dose of 50 kGy (5 Mrad) at an accelerating voltageof 165 kV to cure the electron beam curable resin composition. Then, 11kinds of decorative sheets were obtained.

The decorative sheets were evaluated by the above-mentioned method. Theevaluation results are shown in Table 1.

TABLE 1 Comparative Examples Examples 1 2 3 4 5 6 7 1 2 3 4 ResinElectron beam 94 94 94 90 87 85 — — — 50 100 composition curable resin AElectron beam — — — — — — 95 — — — — curable resin B Electron beam 6 6 —10 10 10 — 100 — 50 — curable resin C Electron beam — — 6 — 3 5 5 — 100— — curable resin D Thickness of 10 20 8 6 8 8 5 8 8 8 8 resincomposition after curing (μm) Examination Three-dimensional AAA AA AAAAA AA AAA AA F F F AA result formability Scratch resistance AAA AAA AAAAA AAA AA AA AA AAA A F (Method A) Scratch resistance AAA AAA AAA AAAAAA AA AA AAA AA A F (Method B)

Note:

Electron beam curable resin A: polycarbonate acrylate with twofunctional groups, weight-average molecular weight: 10,000Electron beam curable resin B: polycarbonate acrylate with sixfunctional groups, weight-average molecular weight: 6,000Electron beam curable resin C: urethane acrylate oligomer with sixfunctional groups, weight-average molecular weight: 6,000Electron beam curable resin D: urethane acrylate oligomer with sixfunctional groups, weight-average molecular weight: 10,000

Examples 8-12 and Comparative Examples 5-8

As the substrate, an ABS resin film (flexural modulus; 2000 MPa,thickness; 400 μm) was used to form a picture layer with a wood grainpattern on the surface of the film by gravure printing using acrylicresin inks. Then, a primer layer consisting of a primer compositioncontaining an acrylic polyol and hexamethylene diisocyanate was coatedon the surface of the picture layer by gravure reverse coating. (Thehexamethylene diisocyanate was mixed in the same NCO equivalent as theOH equivalent of the acrylic polyol). The thickness of the primer layerwas 3 μm.

Then, the electron beam curable resin composition shown in Table 2 wascoated on the surface of the primer layer by gravure coating so that thethickness (μm) of the resin composition after curing is as described inTable 2. This uncured resin layer was irradiated with electron beamswith an irradiation dose of 50 kGy (5 Mrad) at an accelerating voltageof 165 kV to cure the electron beam curable resin composition. Then, 9kinds of decorative sheets were obtained.

The decorative sheets were evaluated by the above-mentioned method. Theevaluation results are shown in Table 2.

TABLE 2 Comparative Examples Examples 8 9 10 11 12 5 6 7 8 ResinElectron beam 70 — — — — 100 — — — composition curable resin E Electronbeam — 70 — — — — — — — curable resin F Electron beam — — 70 70 50 — 100— 30 curable resin G Electron beam 30 30 30 — — — — 100 — curable resinH Electron beam — — — 30 50 — — — 70 curable resin I Thickness of 7 7 710 10 7 7 7 33 resin composition after curing (μm) ExaminationThree-dimensional AA AA AA AA AA F F F A result formability Chemicalresistance AA AA AA AA AA AA F AA F Scratch resistance AA AA AA AA AA FF AA F (Method B)Electron beam curable resin E: acrylic silicone acrylate, weight-averagemolecular weight: 20,000, mean molecular weight between cross-linkingpoints: 100Electron beam curable resin F: acrylic silicone acrylate, weight-averagemolecular weight: 20,000, mean molecular weight between cross-linkingpoints: 200Electron beam curable resin G: acrylic silicone acrylate, weight-averagemolecular weight: 20,000, mean molecular weight between cross-linkingpoints: 400Electron beam curable resin H: urethane acrylate oligomer with sixfunctional groups, weight-average molecular weight: 5,000, Young'smodulus of cured coating film of ionizing radiation curable resincomposition: 800 MPaElectron beam curable resin I: urethane acrylate oligomer with twofunctional groups, weight-average molecular weight: 15,000, Young'smodulus of cured coating film of ionizing radiation curable resincomposition: 200 MPa

The decorative sheets of Examples 1-12 of the present inventionexhibited excellent three-dimensional formability without no cracksbeing generated in typical insert molding and simultaneousinjection-molding and decoration, even under the condition of rapidtemperature drop from a heating temperature of about 160° C. to that atthe contact with a mold, a rapid extension rate, and a high degree ofdrawing. It was confirmed that the surfaces of the produced decorativeresin-molded articles had high scratch resistance.

Furthermore, it was confirmed that the decorative sheets of Examples8-12 had high chemical resistance.

INDUSTRIAL APPLICABILITY

The decorative sheet of the present invention is used for variousdecorative resin-molded articles, suitably for use in, for example, theinternal or exterior material of a vehicle such as an automobile;carpentry members such as a base board and a cornice; fittings such as awindow and a door frames; internal materials in a building, such as awall, a floor, and a ceiling; housings for home electric appliances suchas a television set and an air conditioner; and a container.

EXPLANATION OF THE CODES

-   10. Decorative sheet-   11. Substrate-   12. Picture layer-   13. Primer layer-   14. Surface protective layer

1. A decorative sheet comprising at least a surface protective layer ona substrate, wherein the surface protective layer includes a curedmaterial of an ionizing radiation curable resin composition at leastcontaining a polycarbonate (A) and a multi-functional (meth)acrylate (B)in a mass ratio (A)/(B) of (98/2)-(70/30), and wherein themulti-functional (meth) acrylate (B) has three or more functionalgroups.
 2. A decorative sheet comprising at least a surface protectivelayer on a substrate, wherein the surface protective layer includes acured material of an ionizing radiation curable resin composition atleast containing an acrylic silicone (meth)acrylate (C) and amulti-functional (meth)acrylate (B) in a mass ratio (C)/(B) of(50/50)-(95/5), and wherein the multi-functional (meth)acrylate (B) hasthree or more functional groups.
 3. (canceled)
 4. The decorative sheetaccording to claim 1, wherein the polycarbonate (A) is apolycarbonate(meth)acrylate (A), and the weight-average molecular weightof the polycarbonate(meth)acrylate (A) is more than 2,000.
 5. Thedecorative sheet according to claim 2, wherein the weight-averagemolecular weight of the acrylic silicone (meth)acrylate (C) is2,000-100,000.
 6. The decorative sheet according to claim 2, wherein themean molecular weight between the cross-linking points of the acrylicsilicone (meth)acrylate (C) is 100-2,500.
 7. A decorative resin-moldedarticle including the decorative sheet according to claim
 1. 8. Adecorative resin-molded article including the decorative sheet accordingto claim
 2. 9. The decorative sheet according to claim 2, wherein theacrylic silicone (meth)acrylate (C) comprises structural units selectedfrom the following formulas (2), (3), and (4):

wherein R¹ represents an alkyl group with 1-4 carbon atoms, R³s are thesame or different from each other, each R³ represents a hydrocarbongroup with 1-6 carbon atoms, R⁴ represents a hydrogen atom or a methylgroup, R⁵ represents an alkyl group or a glycidyl group, R⁶ representsan organic group with a (meth)acryloyloxy group, and n is an integer.